It is commonly known that a patient monitoring apparatus is used for monitoring a physiological parameter of a patient, in order to continuously supervise a health state of the patient. Usually, the patient monitoring apparatus comprises an alarm device configured for providing an alarm signal in those cases in which a sensed value of the monitored physiological parameter deviates from values of a predefined interval. In particular, an alarm signal is generated in cases in which the sensed value is less than or at most equal to a lower alarm limit and in cases in which the sensed value exceeds an upper alarm limit. The lower and upper alarm limits may depend on the age of the patient, the kind of monitored physiological parameter, and general guidelines defined by a supervision unit owning or operating the patient monitoring apparatus.
It is further known that a supplementary treatment may be administered to the patient during the monitoring of the physiological parameter, in order to guarantee a proper health state of the patient and/or to improve the health state of the patient. The administration of the treatment may influence the sensed value of the monitored physiological parameter of the patient. In particular, the sensed physiological parameter value may decrease or increase, respectively, causing the sensed value of the physiological parameter to be lower than the lower alarm limit or to exceed the upper alarm limit of the alarm device of the patient monitoring apparatus, respectively. Accordingly, the lower and upper alarm limits of the alarm device may represent particularly important parameters during monitoring the patient, since the lower and upper alarm limits may represent safety relevant issues for the patient.
For example, arterial hemoglobin oxygen saturation (SpO2) of a preterm infant may be monitored using a patient monitoring apparatus during the first days after the birth of the infant, in order to guarantee a proper physical development of the infant. A deviation of the oxygen saturation value of the infant from a range of predefined values for a given time may impact the health of the infant. For example, a too low value of the oxygen saturation (hypoxemia) may result in hypoxia of the brain and other organs, which may lead to permanent damage of these organs. For a preterm infant, the lower SpO2 alarm limits of an alarm device may be defined by individual hospital definitions and may correspond to about 88%.
Further, a treatment agent in the form of supplementary oxygen may be supplied to the preterm infant, to ensure a sufficient oxygen saturation value of the infant. On the other side, supplying too much oxygen to the infant may increase the incidence of retinopathy of prematurity (ROP) and lung disease. During a time in which the infant may receive supplementary oxygen, an increased diligence of a caregiver of the infant may be required to prevent diseases of the infant resulting from too high oxygen saturation values. This may be achieved by avoiding oxygen saturation levels in the upper range (hyperoxemia). Typically this may be accomplished by using the upper SpO2 alarm limit of an alarm device. The upper SpO2 alarm limits of an alarm device may be defined by individual hospital definitions and may correspond to about 94%, a saturation value which is of no concern when the infant is breathing normal air.
By using the standard low and high SpO2 alarm limits, it may happen that nuisance alarm signals are triggered by a sensed hemoglobin oxygen saturation value exceeding the upper alarm limit although no supplementary oxygen is supplied to the infant.
In order to adapt the personal monitoring of a caregiver of the infant to the fact whether the infant is receiving oxygen or not, it is known from the medical survey “Which oxygen saturation level should we use for very premature infants? A randomized controlled trial”, BOOSTII, NHMC Clinic Trials Center, 24 Aug. 2006, that the upper alarm limit of an alarm device shall be set to 94% in case a monitored infant receives supplementary oxygen and that the upper alarm limit of the alarm device shall be switched off or deactivated in cases in which the infant is exposed to air.
Further, it is known from NICU Specific policies “Pulse Oximetry”, Proc17.23, issued in July 1992 and revised in July 2000, that a high Sp02 alarm is to be deactivated in cases in which the patient is exposed to room air or is a full term infant and that a high Sp02 alarm is to be set to 98% in cases in which the patient is a preterm infant and is receiving oxygen.
However, such a manual controlling of the upper alarm limit may result in a time consuming supervision of the infant, since the caregiver of the infant may have to permanently monitor the individual treatment of the infant. Further, a potential risk of health threats of the infant may be increased using the above described controlling of the state of the upper alarm limit of the alarm device.